U.S. patent application number 11/141771 was filed with the patent office on 2005-12-01 for elastomeric magnetic nanocomposite biomedical devices.
Invention is credited to Shadduck, John H..
Application Number | 20050267321 11/141771 |
Document ID | / |
Family ID | 35426279 |
Filed Date | 2005-12-01 |
United States Patent
Application |
20050267321 |
Kind Code |
A1 |
Shadduck, John H. |
December 1, 2005 |
Elastomeric magnetic nanocomposite biomedical devices
Abstract
A biomedical device of a smart elastomer, more particularly
relating to a class of low modulus elastomers with dispersed,
aligned magnetic nanoparticles therein that allow for controlling
the flexural modulus of the device and engaged tissue in response
to an applied magnetic field. An exemplary embodiment is used for
treating obstructive airway syndrome wherein one or more implants
including an elastomer magnetic nanocomposite are placed in a
patient's soft palate. During sleep, a source of magnetic flux is
applied to stiffen the implants to dampen vibrations in tissue
which occur in snoring and sleep apnea episodes. The magnetic flux
is provided by a permanent magnet or by a magnetic field source
coupled to a controller for modulating the stiffness of the
implant(s). In similar embodiments, the controlled modulus implants
can be used to treat various anatomic structures such as upper
airway tissue, oral cavity tissue, gastrointestinal tract tissue,
urinary tract tissue, cardiovascular tissue, muscle tissue, penile
tissue, sphincters and skin.
Inventors: |
Shadduck, John H.; (Menlo
Park, CA) |
Correspondence
Address: |
John H. Shadduck
350 Sharon Park Drive #B23
Menlo Park
CA
94025
US
|
Family ID: |
35426279 |
Appl. No.: |
11/141771 |
Filed: |
June 1, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60575984 |
Jun 1, 2004 |
|
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Current U.S.
Class: |
600/12 |
Current CPC
Class: |
A61N 2/06 20130101; A61F
5/56 20130101; A61N 2/00 20130101; A61F 5/0079 20130101 |
Class at
Publication: |
600/012 |
International
Class: |
A61N 002/00; A61M
037/00 |
Claims
What is claimed is:
1. A therapeutic method for controlling a property of mammalian
body structure comprising implanting an elastomeric magnetic
composite in targeted body structure and applying magnetic flux
thereby altering a property of the composite and the targeted body
structure.
2. The therapeutic method of claim 1 wherein applying magnetic flux
alters at least one property selected from the group of stiffness,
elasticity, resilience and elastic modulus.
3. The therapeutic method of claim 1 wherein the targeted body
structure is within tissue in at least one of the upper airways,
the oral cavity, the gastrointestinal tract, the urinary tract,
cardiovascular tissue, muscle tissue, sphincters, penile tissue or
skin.
4. The therapeutic method of claim 1 wherein applying magnetic flux
damps vibrations in the body structure.
5. The therapeutic method of claim 1 wherein applying magnetic flux
supports body structure to thereby prevent laxity in the body
structure.
6. The therapeutic method of claim 1 wherein applying magnetic flux
is accomplished by means of a permanent magnet or a magnetic flux
generator.
7. The therapeutic method of claim 1 wherein applying magnetic flux
includes controlling parameters selected from the group of field
strength and duration with a controller.
8. The therapeutic method of claim 1 wherein applying magnetic flux
includes modulating the application of magnetic flux in response to
a signal from at least one of an acoustic sensor, a pressure
sensor, an electrical signal sensor, an accelerometer and a light
sensor.
9. A biomedical device comprising a body configured for coupling to
mammalian anatomic structure, the body including an elastomeric
composite having an elastic modulus that differs by more than 20%
when under the influence of applied magnetic flux as compared to
the elastic modulus when not under the influence of magnetic
flux.
10. The biomedical device of claim 9 wherein the elastic modulus
differs by more than 40% when under the influence of applied
magnetic flux as compared to the elastic modulus when not under the
influence of magnetic flux.
11. The biomedical device of claim 9 wherein the elastic modulus
ranges between about 5 kPa and 5 MPa when not under the influence
of magnetic flux.
12. The biomedical device of claim 9 wherein the body is configured
for coupling to tissue selected from the group of upper airway
tissue, oral cavity tissue, the gastrointestinal tract tissue,
urinary tract tissue, cardiovascular tissue, muscle tissue,
sphincter tissue, penile tissue or skin.
13. The biomedical device of claim 9 wherein the elastomeric
composite has an elastic modulus ranging between 5 kPa and 5 MPa
when not under the influence of the magnetic flux.
14. The biomedical device of claim 9 wherein the elastomeric
composite includes at least one of ferromagnetic, paramagnetic or
superparamagnetic elements magnetically aligned in an
elastomer.
15. The biomedical device of claim 14 wherein the elements have a
mean cross-section ranging between 10 nm and 100 microns.
16. The biomedical device of claim 14 wherein the elastomer is at
least one of a silicone, a polyurethane, a polyolefin, a
polybutadiene, a natural rubber or a hydrogel.
17. A biomedical system comprising a biocompatible implant body
configured for implantation in mammalian tissue, the body including
an elastomer magnetic composite and a source of magnetic flux.
18. The biomedical system of claim 17 wherein the implant body has
a selected shape in which the elastomer magnetic composite includes
magnetically aligned elements carried therein.
19. The biomedical system of claim 17 wherein the implant body
includes a shape memory polymer.
20. A biomedical system as in claim 17 wherein the source of
magnetic flux is a magnet or a magnetic flux generator.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims benefit of Provisional U.S. Patent
Application Ser. No. 60/575,984 filed Jun. 1, 2004 titled
Elastomeric Magnetic Nanocomposite Biomedical Devices, which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to smart elastomers for biomedical
devices and more particularly relates to a class of low modulus
elastomers with dispersed, magnetically aligned nanoparticles
therein that can provide for controlled flexural modulus in
response to an applied magnetic field. In an exemplary method of
use, biomedical implants of the elastomer magnetic composite can be
placed in a patient's soft palate to dampen vibrations in the
tissue when sleeping in a treatment for obstructive airway
syndrome, which included sleep apnea and snoring.
[0004] 2. Background of the Invention
[0005] There are many clinical needs for altering the deformability
of elastic tissues and body structures. In all cases, the prior art
has been directed to inventions that are adapted for static tissue
modifications. For example, numerous inventions relate to "tissue
bulking" by means of various injectable materials and by means of
creating "stiffening" lesions in tissue. Such lesions have been
created by thermotherapies, cryotherpies and chemotherapies. In
such so-called tissue-bulking therapies, the objective often is to
alter a mechanical property of targeted tissue, such as stiffness,
flexibility or more generally elasticity.
[0006] Several surgical procedures utilize such tissue-bulking
methods. For example, in the field of sleep apnea and snoring,
various thermal treatments and implanted materials have been
proposed for creating stiffened regions in the soft palate. In
other procedures, tissue-bulking has been developed for treating
sphincter tissues to assist in sphincter closure. In the field of
urinary incontinence treatments, both injectable materials and
thermal treatments have been developed for bulking the periurethral
tissues and spaces. In the gastrointestinal field, various
injectables and thermal treatments are used for altering the
flexibility of the lower esophageal sphincter (LES) to treat
gastroesophageal reflux disease (GERD). It has been suggested that
the pyloris can be bulked-up with injectables to increase the
gastric retention period in a strategy to treat morbid obesity.
Other bulking treatments are proposed for treating fecal
incontinence by thermally-created lesions in anal sphincter
tissue
[0007] In all of the prior art devices and methods, the only result
of the various treatments consists of a tissue mass that has a
different "static" mechanical property--for example, a stiffer,
less flexible tissue. What is needed for treating many disorders
that relate to tissue flexibility is a system and method for
controlled, dynamic adjustment of the elastic properties of
targeted tissues.
[0008] Obstructive airway syndrome sleep apnea and snoring. To
understand the related art as well as to understand one embodiment
of the invention disclosed herein, it is useful to refer to views
of a patient's airways as shown in FIG. 1A. In normal breathing,
air passes through a patient's nose or mouth and past soft flexible
anatomic structures such as the base of the tongue on one side and
the soft palate, uvula, and tonsils on the other. When awake, the
patient's muscles around the above-described anatomic structures
tighten to prevent the structures from obstructing the patient's
air passageways. During sleep, the patient's muscles relax but
generally the anatomic structures still do not prevent air from
flowing freely into and out of the patient's lungs. Snoring occurs
when anatomic structures in the throat (e.g., base of the tongue,
soft palate and uvula) are lax (as when a patient's muscles
over-relax) and collapse during sleep to partly obstruct the
passage of air. Referring to FIG. 1A, when air passes the partly
obstructed area (air flow indicated by arrows), it can be seen that
the lax anatomic structures vibrate or impact each other resulting
in the sounds of snoring.
[0009] The more serious obstructed airway syndrome results in sleep
apnea ("apnea" meaning no breathing). Referring again to FIG. 1A,
the anatomic structures may entirely block the air passageways from
both the nose and mouth. During an apnea episode, the brain will
cause the patient to awaken since air is not reaching the lungs.
The patient typically will awaken abruptly thus causing the muscles
around the lax structures in the throat to tighten and remove the
obstructions to the air passageway. The patient typically emits a
gasp and then breathing begins again. Such apnea episodes may
continue throughout the night, resulting in fragmented nonrestful
sleep. An apnea patient typically will feel tired during the day,
even though he or she may not recall the waking episodes. Further,
such lack of air supply to the lungs can strain the patient's lungs
and heart--possibly leading to disorders such as high blood
pressure, heart attack or stroke.
[0010] Non-surgical treatments for sleep apnea and severe snoring
include a continuous positive air pressure (CPAP) device which has
a small blower connected by a flexible hose to a mask. The blower
sends a steady stream of air through the patient's nose and throat
to prevent the soft structures in the throat from collapsing to
obstruct the airway. Such CPAP devices have the disadvantages of
being inconvenient, being necessary all night (every night) and
requiring adjustment over time as the patient changes weight, etc.
Other treatments for mild forms of sleep apnea include a wide range
of shaped oral devices. Specially trained dental professionals
cooperate with sleep disorder specialists to design devices that
(i) may hold the tongue forward to prevent it from blocking the
throat, (ii) may hold the entire jaw forward, or (iii) may lift the
soft palate and uvula to keep such structures from blocking the
throat.
[0011] Several types of surgery have been developed to prevent
sleep apnea or to alleviate snoring. Most such surgeries are
adapted to increase the cross-section of the airway by removing
anatomic structures or tissues from around the patient's throat.
The most common surgery for sleep apnea and snoring is
uvulopalatopharyngoplasty (UPPP) in which the tonsils, uvula and
part of the soft palate are resected from the patient's throat.
Still, a UPPP is not entirely successful in treating sleep apnea
since tissues further back in the throat and at the base of the
tongue may still block the passage of air. More recently,
laser-assisted uvulopalatoplasty (LAUP) has been developed which is
considered appropriate only for snoring since the procedure does
not remove all tissues that may block the airways. In a LAUP, the
physician uses a laser to cut out part or all of the uvula and a
portion of the soft palate. The disadvantages of UPPP and LAUP
procedures are significant and include bleeding, infection, tongue
numbness, voice change, food and liquid flow into the nasal
passageway during swallowing, and possible failure to cure sleep
apnea leading to apnea without snoring ("silent apnea").
[0012] The above invasive surgeries do not treat a key aspect of
obstructive airway disorders--the large volume of lax tissue
typically found around the base of the patient's tongue. Tissue
resections around the base of the tongue are not attempted because
of difficulty of access as well as surgical risks mentioned above.
Two types of surgeries relating to the tongue are known for
treating sleep apnea. Both surgeries are very invasive and risky.
In one type of surgery, the patient's jaw is detached and moved
forward to make the air passageway larger beyond the base of the
tongue. In a second type of surgery, the tongue attachments are
severed and the tongue is re-attached in a more forward position to
increase the dimension of the air passageway beyond the base of the
tongue.
[0013] Improved methods for treating sleep apnea (and obstructive
airway syndrome, in general) are needed. In particular, treatments
that deal with lax tissues in the soft palate and around the base
of the patient's tongue are needed. Preferably, the improved
methods are less invasive than current surgical approaches.
SUMMARY OF THE INVENTION
[0014] The present invention relates to implants, biomedical
devices and techniques for in-situ adjustment of the flexural
modulus of anatomic structures in human patients to treat various
disorders.
[0015] The biomedical devices or implants of the invention include
an elastomeric nanocomposite body with a flexural modulus that can
be controlled by an applied magnetic field. An elastomeric magnetic
nanocomposite (ENM) is fabricated by dispersing and magnetically
aligning nanometric magnetic particles in a crosslinked polymeric
matrix. During the crosslinking or curing of the elastomer, the
nanoparticles are maintained in a selected orientation. The
nanocomposite when not under the influence a magnetic flux can have
a very low flexural modulus. Thereafter when in use, variable
levels of magnetic flux can be applied to increase the stiffness of
the monolith, as well as urge the monolith toward its memory shape.
In use, controlled magnetic fields or mechanical perturbations can
induce the nanoparticles within the composite to align along the
lines of flux.
[0016] In one exemplary embodiment, the implant and techniques can
be used to treat the symptoms of sleep apnea or OAS (obstructed
airway syndrome) which includes snoring. The implants can be placed
in airway tissue to dynamically stiffen relaxed tissues in the soft
palate or around the base of the patient's tongue for intervals
during sleep. The novel treatment is adapted to replace more
invasive surgical methods, such as (i) conventional
uvulopalatopharyngoplasty (UPPP), or (ii) laser-assisted
uvulopalatoplasty (LAUP) both of which include resection of lax
airway tissues.
[0017] The description of one exemplary embodiment in the field of
OAS is not limiting, and is merely used as explanatory tool to
describe a single type of implant in more detail. The invention has
equally important uses in treating cardiovascular disorders, GI
tract disorders, urinary tract disorders, overeating disorders, and
other treatments and therapies described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The features and advantages of this invention, and the
manner of attaining them, will become apparent by reference to the
following description of preferred embodiments of the invention
taken in conjunction with the accompanying drawings, wherein:
[0019] FIG. 1A is a sectional view of the anatomic structures of a
patient's upper airway tract showing the symptoms of sleep apnea or
obstructed airway syndrome, and further illustrating the elastomer
magnetic nanocomposite implant corresponding to the invention.
[0020] FIG. 1B is a frontal view of the patient's soft palate
illustrating exemplary locations of the elastomeric magnetic
nanocomposite implants.
[0021] FIG. 2A is a perspective view of an elastomeric magnetic
nanocomposite implants of a shape memory polymer in a memory
shape.
[0022] FIG. 2B is a perspective view the implant of FIG. 2A in a
temporary shape.
[0023] FIG. 3 is a cut-away view of a patient's stomach
illustrating the implantation of at least one elastomeric magnetic
composite implant in a patients lower esophageal sphincter
(LES).
[0024] FIG. 4 is a cut-away view of a patient's stomach
illustrating the implantation of EMN implants in a the fundus of
the stomach for treating obesity.
[0025] FIG. 5 is a view of a portion of a gastrointestinal tract
illustrating the implantation of at least one elastomeric magnetic
nanocomposite implant in the pyloric sphincter.
DETAILED DESCRIPTION OF THE INVENTION
[0026] FIGS. 1A-1B and 2A-2B illustrate an exemplary embodiment of
elastomer magnetic nanocomposite (EMN) and it method of use. The
implant bodies 100A are shaped and formed for vibration damping in
a patient's upper airway structures to treat obstructed airway
syndrome (OAS) or more generally sleep apnea and snoring. The
elastomer material comprises a new class of biocompatible smart
material with a modulus that can be controlled by an applied
magnetic field. The more detailed description of the use of an
exemplary implant body 100A in treating a patient's airway tissue
is not limiting, and is but one example of a number of uses in a
human patient for dynamic stiffening of tissue or for controlling
the flexural modulus of a target mammalian body structure.
[0027] In this disclosure, the terms "modulus" and "elastic
modulus" are used to describe the flexibility and elastic
properties of a composite material, and the combination of the
material and engaged tissue, that can be "altered" in response to
applied magnetic flux. The terms "modulus" and "elastic modulus"
are use interchangeably with more specific modulus definitions such
as Young's modulus and flexural modulus. In general, the system
corresponding to the invention can dynamically adjust mechanical
properties of a viscoelastic composition, and it is unnecessary to
more specifically define the targeted modulus parameters. Young's
modulus is the ratio between stress and strain, i.e., stress
divided by strain wherein stress is the force per unit area acting
on a material which tends to change its dimensions. Among other
types, stress can be tensile as when the body is subject to a
tension load, compressive as when the body is subject to
compression loading, or shear as when the body is subject to a
shearing load. Flexural modulus is the ratio of stress to strain
within the elastic limit and is similar to the tensile modulus.
Flexural modulus is used to indicate the bending stiffness of a
material.
[0028] One preferred method of treating airway tissue is to insert
at least one implant body 100A (and preferably from about 2 to 6
implants) of an elastomer magnetic nanocomposite (EMN) in the
patient's soft palate tissue 102 as illustrated in FIGS. 1A and 1B.
In FIG. 1A, the palate 108 separates the oral cavity 110 from the
nasal cavity 112. The anterior region of the palate comprises the
bony hard palate 114. The soft palate 102 comprises muscles and
soft tissue and is suspended from the posterior portion of hard
palate 114. The posterior margin of the soft palate is free to move
or vibrate and terminates in the uvula 116 which droops into the
posterior oral cavity and airway.
[0029] Referring to FIG. 1A, the soft palate 102 and uvula 116 are
unsupported by cartilage and during sleep the muscles can relax
causing these tissues to sag into the airway. The resulting airflow
can cause the soft palate and uvula to vibrate which results in
snoring. The soft palate and tongue also can relax sufficiently
during sleep to partially or fully obstruct the airway. Such
obstructive airway syndrome (OAS) can result in hypopnea wherein
the airway is partially obstructed or apnea wherein the airway is
completely obstructed. Sleep apnea, and to a lesser degree,
hypopnea can have extremely serious health consequences.
[0030] In FIGS. 1A and 1B, the implants 100A have a modulus when
free of magnetic flux that is similar to the native tissue, or is
less than the native tissue, in which the implant bodies are
implanted. For example, the elastic modulus can be from about 5 kPa
to 5000 kPa and more preferably from about 20 kPa to 2000 kPa when
not under the influence of a magnetic field or magnetic flux. In
this condition, the implants would not be noticed by the patient,
in terms of flexibility.
[0031] In an exemplary embodiment, the elastomer component of the
nanocomposite comprises from about 30% to about 99% of the material
by weight or volume, and can be any biocompatible elastomer. For
example, the elastomer can comprise a cross-linked polymeric gel
having the selected modulus described above and can be a thermoset
or thermoplastic polymer. Suitable elastomers can comprise a
silicone, a polyurethane, a hydrogel, a polyamide, a polyester, or
another suitable elastomer or a combination of the above polymers.
Additionally, other non-polymeric compositions can be dispersed
within the nanocomposite, for biocompatibility, for prevention of
tissue adherence, for antibiotic or other drug release, etc.
[0032] In an exemplary embodiment, the magnetically responsive
particles or nanoparticles that are carried within the elastomer
can be any suitable elements known in the art. The particle
component of the composite can consist of any solid material which
exhibits magnetic activity, for example any material, alloy or
compounds which exhibits ferromagnetic, paramagnetic or
superparamagnetic properties. Such particles or nanoparticles can
be of iron, iron oxide, iron nitride, iron carbide, carbonyl iron,
chromium dioxide, low carbon steel, silicon steel, nickel, cobalt,
and mixtures thereof. Iron oxide includes all known pure iron
oxides, such as ferric and ferrous oxides, e.g., ferrites and
magnetites. The magnetic particles also comprise of alloys of iron,
such as those containing aluminum, silicon, cobalt, nickel,
vanadium, molybdenum, chromium, tungsten or manganese. Typically,
the magnetic elements are in the form of metal powders prepared by
processes well known to those skilled in the art. Many methods are
available for the manufacture of metal powders, including laser
pyrolysis, grinding, attrition, electrolytic deposition, metal
decomposition, etc. Various metal powders are commercially
available, including iron powders. In one embodiment, the particles
can be iron powders, iron oxide powders or mixtures thereof and
iron oxide powders and reduced iron powder mixtures. Also, reduced
carbonyl iron particles are useful.
[0033] In preferred embodiments, the magnetic responsive elements
are dispersed within the polymer when the polymer is in a liquid
state, and the elements are then magnetically aligned with a very
strong magnetic field as the elastomer polymerizes into a composite
having the modulus described above. The elastomer can have any
selected form or shape in which the magnetic responsive are
aligned. Thus, the implant can be described as having a magnetic
alignment shape under the influence of magnetic flux. In
alternative embodiments, an implant body can have a uniform density
or gradient in density of the magnetic particles across the implant
volume. A gradient in density allows for the response of the
"altered" modulus under the influence of magnetic flux to be
graduated along or about an axis of the implant body.
[0034] The magnetic particle dimensions will have an influence on
the response of the material to magnetic flux, and the particles
have a mean cross-section ranging between 5 nm to 500 microns, and
more preferably a mean cross-section ranging between about 10 nm
and 100 microns. In a preferred embodiment, the magnetic responsive
elements are non-spherical. Preferably, the magnetic responsive
elements or nanoparticles are highly elongated. By this means, the
nanoparticles will be more securely embedded in the low modulus
elastomer matrix. High aspect ratio nanoparticles are fabricated by
Nanogram Corporation, 2911 Zanker Road, San Jose, Calif. 95134.
[0035] While the implants are described above as treating tissue by
altering the modulus or stiffness of the implant body and the
engaged body structure, it is also accurate to describe the implant
as being "actuated" or urged from a flexed shape toward its memory
or magnetic alignment shape. Thus, the scope of the invention
encompasses moving an implant body coupled to an anatomic structure
toward the memory shape of an elastomer magnetic nanocomposite of
the implant body.
[0036] In an exemplary embodiment, the scope of the invention
encompasses an elastomeric nanocomposite wherein the composite has
an elastic modulus that differs by more than 20% when under the
influence of applied magnetic flux as compared to the elastic
modulus when not under the influence of magnetic flux. More
preferably, the nanocomposite has an elastic modulus that differs
by more than 40% when under the influence of applied magnetic flux
as compared to the elastic modulus when not under the influence of
magnetic flux.
[0037] FIG. 1A shows a method of use the implant wherein magnetic
flux MF can increase the flexural modulus of the implant 100A to
stiffen the soft palate during sleep when the muscles relax. In one
embodiment, the patient can wear a collar or other similar
apparatus at night that carries magnetic flux means, for example,
rare earth Neodymium-Iron-Boron (NIB) magnets. Such NIB magnets are
very strong and one or more such magnets can be provided within a
protective collar-like apparatus. During the patient's awake hours,
the collar-like apparatus would not be worn and the patient would
not notice the flexible filament implants. This system embodiment
when worn by the patient would operate in an "always-on" mode as
long as the magnetic flux is within range of the implant to thereby
stiffen the soft palate.
[0038] In another embodiment, the system can use a magnetic field
generator and controller for creating selected magnetic field
levels and on-off intervals of magnetic flux to actuate or stiffen
the implants 100A of FIGS. 1A-1B. The system can coupled to a
sensor, for example, to stiffen the implants in response to the
sound of snoring, or an electrode sensor that can sense electrical
pattern or respiratory patterns that indicate a sleep apnea
episode. The system can further control magnetic flux dosimetry in
cooperation with feedback circuitry sensors again linked to
electrical or respiratory signals. It should be appreciated that
the application or modulation of magnetic flux can be linked to
signals from any type of sensor, such an acoustic sensor, a
pressure sensor, an electrical signal sensor, an accelerometer or a
light sensor.
[0039] In one embodiment of airway implants depicted in FIGS. 2A
and 2B, the elastomer component is of a shape memory polymer (SMP)
that has a stress-free memory shape (FIG. 2B) and can formed into
an internally-strained temporary shape (FIG. 2A). The implant can
be a ribbon or filament having any cross-sectional shape for needle
injection or insertion in the soft palate or the base of the
tongue. At least one end of the implant 121a or 121b can have an
increased cross-section memory shape for serving as a soft "barb"
to prevent its migration after implantation. The implant still can
be explanted easily. The implant also can be surface modified to
prevent tissue ingrowth to allow for its extraction. In another
strategy, the surface can textured for preventing migration, or
have a slightly porous surface to enhance tissue ingrowth to
prevent migration. The implants can be singular or plural and in
any suitable shape, for example in the form of ribbons, filaments,
flexible rods, discs and the like.
[0040] As background, the class of shape memory polymers (SMPs) of
interest herein comprises a type of co-polymer that consists of a
hard segment and a soft segment each having a different glass
transition temperature. One segment has a glass transition
temperature ranging between about 35.degree. C. and 80.degree. C.
at which the shape memory polymer changes from a first dimension or
volume to a second dimension or volume. For example, after
implantation in tissue one segment of the polymer can have a glass
transition temperature of about 35.degree. C. to 37.degree. so that
body temperature causes the implant to self-deploy from an initial
temporary shape to an expanded memory shape.
[0041] The shape memory polymers (SMPs) used in the implant body
100A (FIGS. 2A-2B) demonstrate the phenomena of shape memory based
on fabricating a segregated linear block co-polymer, typically of a
hard segment and a soft segment. The shape memory polymer generally
is characterized as defining phases that result from glass
transition temperatures in the hard and soft segments. The hard
segment of SMP typically is crystalline with a defined melting
point, and the soft segment is typically amorphous, with another
defined transition temperature. In some embodiments, these
characteristics may be reversed together with the segment's glass
transition temperatures.
[0042] In one embodiment, when the SMP material is elevated in
temperature above the melting point or glass transition temperature
of the hard segment, the material then can be formed into a memory
shape. The selected shape is memorized by cooling the SMP below the
melting point or glass transition temperature of the hard segment.
When the shaped SMP is cooled below the melting point or glass
transition temperature of the soft segment while the shape is
deformed, the temporary shape is then fixed. The original shape is
recovered by heating the material above the melting point or glass
transition temperature of the soft segment but below the melting
point or glass transition temperature of the hard segment. (Other
methods for setting temporary and memory shapes are known which are
described in the literature below). The recovery of the original
memory shape is thus induced by an increase in temperature, and is
termed the thermal shape memory effect of the polymer. The
transition temperature can be body temperature or somewhat below
37.degree. C. in many embodiments--or a higher selected temperature
when the implant body is adapted to cooperate with magnetic
responsive particles or chromophores in the polymer that cooperate
with a remote energy source.
[0043] The implant body 100A of FIG. 2A can change shape to the
form of FIG. 2B at body temperature. Alternatively, the implant
body 100A can carry any suitable biocompatible material that
cooperates with photonic energy, electrical energy or magnetic
energy to elevate its temperature. Light sources, Rf sources and
magnetic emitters are known and can be used to deliver energy to
the implant, e.g., as disclosed in the author's U.S. patent
application Ser. No. 09/473,371 filed Dec. 27, 1999 (now U.S. Pat.
No. 6,306,075), incorporated herein by reference. The detail of the
energy source need not be further described herein. The application
of energy from any source can be used with an implant that is
designed to have a transition temperature anywhere above about
37.degree. C.--for example, in a range extending from about
37.degree. to 80.degree. C. The step of elevating the temperature
of an implant component is typically performed immediately after
implantation, but the scope of the invention includes using
magnetic resonant means, for example, at a later time to expand the
implant component or alter the component's ability to diffuse
water, or to alter other functional parameters.
[0044] Besides utilizing the thermal shape memory effect of the
polymer, the memorized physical properties of the SMP can be
controlled by its change in temperature or stress, particularly in
ranges of the melting point or glass transition temperature of the
soft segment of the polymer, e.g., the elastic modulus, hardness,
flexibility, and permeability. The scope of the invention of using
SMPs in implants extends to the control of such physical properties
within the implant for numerous therapeutic applications.
[0045] Examples of polymers that have been utilized in hard and
soft segments of SMPs include polyethers, polyacrylates,
polyamides, polysiloxanes, polyurethanes, polyether amides,
polyether esters, and urethane-butadiene copolymers. See, e.g.,
U.S. Pat. No. 5,145,935 to Hayashi; U.S. Pat. No. 5,506,300 to Ward
et al.; U.S. Pat. No. 5,665,822 to Bitler et al.; and U.S. Pat. No.
6,388,043 to Langer et al, all of which are incorporated herein by
reference. SMPs are also described in the literature: Ohand Gorden,
Applications of Shape Memory Polyurethanes, Proceedings of the
First International Conference on Shape Memory and Superelastic
Technologies, SMST International Committee, pp. 115-19 (1994); Kim,
et al., Polyurethanes having shape memory effect, Polymer
37(26):5781-93 (1996); Li et al., Crystallinity and morphology of
segmented polyurethanes with different soft-segment length, J.
Applied Polymer 62:631-38 (1996); Takahashi et al., Structure and
properties of shape-memory polyurethane block copolymers, J.
Applied Polymer Science 60:1061-69 (1996); Tobushi H., et al.,
Thermomechanical properties of shape memory polymers of
polyurethane series and their applications, J. Physique IV
(Colloque Cl) 6:377-84 (1996)) (all of the cited literature
incorporated herein by this reference).
[0046] Of particular interest, the use of an open structure of a
shape memory polymer provides several potential advantages in
implants, for example, very large shape recovery strains are
achievable, e.g., a substantially large reversible reduction of the
Young's Modulus in the material's rubbery state; the material's
ability to undergo reversible inelastic strains of greater than
10%, and preferably greater that 20% (and up to about 200%-400%);
shape recovery can be designed at a selected temperature between
about 30.degree. C. and 45.degree. C., and injection molding is
possible thus allowing complex shapes. These polymers demonstrate
unique properties in terms of capacity to alter the material's
water or fluid permeability, thermal expansivity, and index of
refraction. However, the material's reversible inelastic strain
capabilities leads to its most important property--the shape memory
effect. If the polymer is strained into a new shape at a high
temperature (above the glass transition temperature T.sub.s) and
then cooled it becomes fixed into the new temporary shape. The
initial memory shape can be recovered by reheating the foam above
its T.sub.s. The shape memory foams are of particular interest for
various implants because they provide even lower density than solid
SMPs.
[0047] In another method and aspect of the invention, referring to
FIG. 3, at least one implant body 100B can be implanted within and
around the LES (lower esophageal sphincter) to allow modulation of
the implant modulus and thus the flexibility, and dimensions of the
sphincter. During and following food intake, or during sleep, the
system can apply magnetic flux to provide an increased modulus
within the implant and LES to prevent gastroesophageal reflux. The
magnetic flux source can be similar to those described above.
[0048] Corresponding to another method and aspect of the invention,
at least one implant body 100C can be inserted into any suitable
layer or layers of the stomach wall, for example interior of the
mucosa or within the muscle layers as depicted in FIG. 4. The
implants can be inserted with a trans-esophageal introducer, but
the scope of the invention includes laparoscopic introduction from
the exterior of the stomach wall. In one embodiment, the implants
can be of a shape memory polymer or a non-shape memory polymer and
have a flattened cross-section in a suitable elongated curved or
straight shape and an elastic modulus to not substantially alter
normal gastric functioning and motility. In this embodiment, a
suitable magnetic flux is applied to the implants from an external
source so the flexural modulus of implants is substantially
increased. It is believed that such controlled stiffening of the
stomach wall, together with the memory shape of the implant, can
mediate the relaxation of stomach muscles in response to afferent
neural signals that follow stretching of smooth muscles caused by a
food bolus within the stomach. It is believed that such mediation
of neurological signals will inhibit relaxation and stretching of
stomach muscles to the extent that stomach volume will be inhibited
during food intake. In another embodiment, magnetic responsive
implants in the stomach wall can be programmed to adjust the
flexural modulus of the implants episodically--which comprises a
different modality than current morbid obesity treatment devices
and methods that create a new static gastric condition (stomach
volume reduction surgery, gastric banding, balloon deployment in
the stomach, ablation of nerves, bulking of pyloris, etc.). The
patient and body tissue can become accustomed to such static
changes in gastric structure and function, which can result in
behavioral adaptation and increased incidence of overeating.
[0049] In another method and aspect of the invention, at least one
implant body can be implanted within and around the pyloris to
allow dynamic modulation of pyloric sphincter flexibility (see FIG.
5). During and following food intake, the system can increase the
modulus of the implant and tissue region to reduce outflows to
thereby increase gastric retention. The patient's feeling of
satiety will thus lead to reduction in food intake.
[0050] The use of dynamically actuated implants of elastomer
magnetic composites can be extended to other fields. For example,
one or more implants can be implanted within and around the anal
sphincter to allow modulation of the implant modulus and thus the
flexibility and dimensions of the sphincter. Fecal incontinence is
the second leading cause of admission to long-term care facilities
in the United States--and is a devastating condition for patients.
While exact data is difficult to obtain, the reported incidence
rate in the general population is from 1-5%, with high rates among
the elderly population. Similar system of implants can be implanted
in, or coupled to, urinary tract tissue to treat incontinence. An
implant of an elastomer magnetic composite corresponding to the
invention can be used to control and stiffen periurethral tissue to
treat stress urinary incontinence. Also, an implant of an elastomer
magnetic composite can be provided in a sheet-like form to couple
to and support uterine tissue in a sling or Burch procedure.
[0051] Another types of elastomer magnetic composite falls into the
type of apparatus that is applied or adhered to the surface of an
organ or body structure for either (i) modulus stiffening and/or
(ii) actuation toward a selected shape. For example, an elastomer
magnetic composite can be inserted in a heart valve wherein the
system is programmed to cause dynamic stiffening of leaflets during
operation of the valve. In operation, a controller would modulate
magnetic flux in response to electrical signals from the heart. In
such an embodiment, a pacemaker would be implanted under the skin
to actuate the device. The implant would alter its modulus upon
actuation as described above, and apply forces to move the implant
toward its memory position, in other words providing "actuator"
functionality.
[0052] In another embodiment, cylindrical members of an elastomer
magnetic composite can function as penile implants to treat
erectile dysfunction. The members can be implanted into the corpora
cavernosa in a minimally invasive procedure and magnetic flux can
be applied to stiffen the members and the engaged tissue to provide
a selected modulus and shape.
[0053] Other types of stiffeners or actuator are possible,
particularly for coupling temporarily or semi-permanently to skin.
In facial treatments, a facial mask including an elastomer magnetic
composite can be adhered gently to a patient for periodic actuation
to stimulate the skin and prevent skin wrinkling. Another
embodiment can be used to apply over the nostrils at night to
function dynamically as a type of breath-right strip for treating
snoring, and can respond to sound. Another embodiment can comprise
a tubular sleeve or stent of an elastomer magnetic composite that
is urged toward a non-collapsed position when under the influence
of magnetic flux. Such an EMN sleeve can be inserted in any body
lumen, such an airway, blood vessel, eustachian tube or the like to
prop open the lumen when under the influence of magnetic flux.
[0054] The above description of the invention intended to be
illustrative and not exhaustive. Those skilled in the art will
appreciate that the exemplary systems, combinations and
descriptions are merely illustrative of the invention as a whole,
and that variations in the dimensions and compositions of invention
fall within the spirit and scope of the invention. Particular
features that are presented in dependent claims can be combined and
fall within the scope of the invention. The invention also
encompasses embodiments as if dependent claims were alternatively
written in a multiple dependent claim format with reference to
other independent claims. Specific characteristics and features of
the invention and its method are described in relation to some
figures and not in others, and this is for convenience only. While
the principles of the invention have been made clear in the
exemplary descriptions and combinations, it will be obvious to
those skilled in the art that modifications may be utilized in the
practice of the invention, and otherwise, which are particularly
adapted to specific environments and operative requirements without
departing from the principles of the invention. The appended claims
are intended to cover and embrace any and all such modifications,
with the limits only of the true purview, spirit and scope of the
invention.
* * * * *